In general, an antenna is a device designed to radiate waves efficiently in a space, or propagate a signal efficiently by receiving waves.
An antenna is fixedly installed to transmit or receive a signal in a predetermined frequency band used for military communication facilities, or to transmit or receive waves used for home appliances such as a TV or a radio. In the fixed state, the antenna transmits and receives signals by resonance in a predetermined frequency band according to a purpose that the antenna serves.
Antennas have recently been developed for mobile devices, black boxes, and so on, which transmit and receive Global Positioning System (GPS) signals, images, voice, and data signals, while moving.
As described above, an antenna capable of transmitting multi-band signals during movement has been developed and used.
Further, in the case where a device is operated by rotating blades, such as a helicopter, an aircraft or drone with propellers, a wind power plant, or a windmill, an antenna is installed for transmitting and receiving various signals configured for monitoring, control, and data according to various purposes.
However, a rotator with blades may interfere with waves transmitted and received from and at an antenna by the blades, thereby decreasing transmission and reception efficiency. Particularly, if the blades are formed of a metal, the metal itself has the property of reflecting waves. The resulting interference occurs to signals transmitted and received by rotation, thereby rapidly decreasing reception efficiency.
Among the rotators, a drone with propellers takes off, flies, and lands by remote control of signals transmitted and received through an antenna. If a signal is blocked or becomes weak during flight, the drone is not controllable and thus collides with an adjacent object or falls down.
Moreover, in the drone with propellers, thrust force and lift force are generated by rotation of propeller blades. As the body of the drone is formed of a metal robust against an external environment, such as aluminum or titanium, the metal interferes with signals transmitted and received from and at the antenna, thus degrading transmission and reception performance and making transmission and reception efficiency fluctuate according to altitudes. As a result, the drone is not controllable.